Php Mysql：通过2个用户ID检索2个用户名

Question

I have one problem that I can't solve. I am doing pair generator for tournament.

I have two tables. The first table contains the usernames and userids. The second table contains match_id, round, user1_id, user2_id

Table 1

user_id  username
21         John
22         Peter
23         Ana
24         Dan


Table 2
match_id  round  user1_id   user2_id
1           1       21          22
2           1       23          24
3           2       21          23
4           2       24          22
.
.
.

And I want to echo

Round 1
John - Peter
Ana - Dan

Round 2
John - Ana
Dan - Peter

Round 3
...

Round 4
...

Can it be done with only one SQL code so I can get both usernames from Table1 for user1_id and user2_id?

To retrieve only one username via user_id I had no problem and its working great:

$sql = "SELECT table1.username, table3.won 
        FROM table1 
        INNER JOIN table3 ON table1.user_id=table3.user_id;";

I know that i could instead of using user_ids in Table2 just use usernames, but I would like to do it this way like I explained above.

Answer 1

select CONCAT((select username from table1 t1 where t.user_id=t1.user_id=t.user_id) ,'-',(select username from table1 t1 where t.user_id=t1.user_id=t.user_id)) from table2 t

OR

 select CONCAT(t1.username,'-',t3.username) from table2 t2
  inner join table1 t1 on t1.user_id=t2.user_id
  inner join table1 t3 on t3.user_id=t2.user_id